DRAFT CHEAT SHEET - WORK IN PROGRESS

Introduction

The .NET Framework

The .NET Framework is Microsoft's principal platform for enterprise development. It is the supporting API for ASP.NET, Windows Desktop applications, Windows Communication Foundation services, SharePoint, Visual Studio Tools for Office and other technologies.

Updating the Framework

The .NET Framework is kept up-to-date by Microsoft with the Windows Update service. Developers do not normally need to run seperate updates to the Framework. Windows update can be accessed at http://windowsupdate.microsoft.com/ or from the Windows Update program on a Windows computer.

Individual frameworks can be kept up to date using NuGet. As Visual Studio prompts for updates, build it into your lifecycle.

Remember that third party libraries have to be updated separately and not all of them use Nuget. ELMAH for instance, requires a separate update effort.

.NET Framework Guidance

The .NET Framework is the set of APIs that support an advanced type system, data, graphics, network, file handling and most of the rest of what is needed to write enterprise apps in the Microsoft ecosystem. It is a nearly ubiquitous library that is strong named and versioned at the assembly level.

Data Access

Use Parameterized SQL commands for all data access, without exception.

Do not use SqlCommand with a string parameter made up of a concatenated SQL String.

Whitelist allowable values coming from the user. Use enums, TryParse or lookup values to assure that the data coming from the user is as expected.

Apply the principle of least privilege when setting up the Database User in your database of choice. The database user should only be able to access items that make sense for the use case.

Use of the Entity Framework is a very effective SQLi prevention mechanism. Remember that building your own ad hoc queries in EF is just as susceptible to SQLi as a plain SQL query.

Encryption

Never, ever write your own encryption. Use the DPAPI for easy access to common algorithms.

When using a hashing function, use a salt value added to the original value before hashing.

Use a strong hash algorithm.

In .NET 4.5 the strongest hashing algorithm is System.Security.Cryptography.SHA512.

Make sure your application can support a change in algorithm.

Use Nuget to keep all of your packages up to date. Watch the updates on your development setup, and plan updates to your applications accordingly.

ASP.NET Web Forms Guidance

ASP.NET Web Forms is the original browser-based application development API for the .NET framework, and is still the most common enterprise platform for web application development.

Always use HTTPS.

Enable requireSSL on cookies and form elements and HttpOnly on cookies in the web.config.

Implement custom errors.

Make sure tracing is turned off.

While viewstate isn't always appropriate for web development, using it provides CSRF mitigation. If you don't use Viewstate, then look to the default master page of the ASP.NET Web Forms default template for a manual anti-CSRF token.

In the Connections pane, go to the site, application, or directory for which you want to set a custom HTTP header.

In the Home pane, double-click HTTP Response Headers.

In the HTTP Response Headers pane, click Add... in the Actions pane.

In the Add Custom HTTP Response Header dialog box, set the name and value for your custom header, and then click OK.

Remove the version header.

<httpRuntime enableVersionHeader="false" />

Also remove the Server header.

HttpContext.Current.Response.Headers.Remove("Server");

HTTP validation and encoding

Do not disable validateRequest in the web.config or the page setup. This value enables the AntiXSS library in ASP.NET and should be left intact to present cross site scripting.

Whitelist allowable values anytime user input is accepted. The regex namespace is particularly useful for checking to make sure an email address or URI is as expected.

Always encode output to the browser using Server.HtmlEncode.

Validate the URI format using Uri.IsWellFormedUriString.

Authorization and authentication

Use cookies for persistence when possible. Cookieless Auth will default to UseDeviceProfile.

Don't trust the URI of the request for persistence of the session or authorization. It can be easily faked.

Reduce the session time from the default of 20 minutes. If slidingExpiration is used this timeout starts after the last request, so active users won't be affected.

Disable slidingExpiration.

Always implement proper access controls.

Compare user provided username with User.Identity.Name.

Check roles against User.Identity.IsInRole.

Use the ASP.NET membership provider and role provider, but review the password storage. The default storage is rather weak. The ASP.NET MVC4 template uses PBKDF2, and is better. Review the OWASP Password Storage Cheat Sheet for more information.

Maintain security testing and analysis on Web API services. They are hidden inside MEV sites, and are public parts of a site that will be found my an attacker. All of the MVC guidance and much of the WCF guidance applies to the Web API.

XAML Guidance

Work within the constraints of Internet Zone security for your application.

Use ClickOnce deployment. For enhanced permissions, use permission elevation at runtime or trusted application deployment at install time.

Windows Forms Guidance

Use partial trust when possible. Partially trusted Windows applications make the attack surface of an application much smaller. Manage a list of what permissions your app must use, and what it may use, and then make the request for those permissions declaratively at run time.

Use ClickOnce deployment. For enhanced permissions, use permission elevation at runtime or trusted application deployment at install time.

WCF Guidance

Keep in mind that the only safe way to pass a request in RESTful services is via HTTP POST, with TLS enabled. GETs are visible in the querystring, and a lack of TLS means the body can be intercepted.

Avoid BasicHttpBinding. It has no default security configuration. Use WSHttpBinding instead.

Use at least two security modes for your binding. Message security includes security provisions in the headers. Transport security means use of SSL. TransportWithMessageCredential combines the two.